Exhaust gas turbochargers are usually employed to increase the performance of piston engines, wherein they increase an air and fuel throughput per work cycle. The exhaust gas turbocharger driven by the exhaust gas flow of the piston engine compresses the air fed to the combustion chamber, wherein, because of different engine operating states, it can be advantageous to decouple the compressed air flow fed to the combustion chamber from the exhaust gas flow, so that more preferably efficiency, response characteristics or operating range of the exhaust gas turbocharger can be improved. Such intervention for controlling the exhaust gas turbocharger can for example be achieved through a variable geometry of the nozzle ducts leading to the turbine wheel.
From DE 102 62 006 B4 an exhaust gas turbocharger with a variable turbine geometry is known, which is realised via a vane mounting ring with guide vanes rotatably mounted thereon/therein, wherein the guide vanes can be adjusted via an adjusting ring mounted coaxially to the vane mounting ring and rotatably with respect to the latter. Here, at least three roller bearings are rotatably mounted on the vane mounting ring, which in turn support the adjusting ring via a respective circumferential groove. Here, the roller bearings supporting the adjusting ring can be exclusively mounted in the vane mounting ring or additionally in a housing part, which improves the mounting but significantly aggravates the installation, that is the assembly.
A further charging device with a variable turbine geometry is known for example from EP 1 009 918 B1.